A group of leading criminal and human rights lawyers has called for an investigation into the security situation in Egypt, over the government’s crackdown on any opposition and the recent mass death sentences for members of the Muslim Brotherhood movement.

The London-based ITN Solicitors, who represent Egypt’s Freedom & Justice Party (FJP) and the country’s Brotherhood-backed ousted president, Mohamed Morsi, made the request on Thursday in a letter addressed to the United Nations Security Council (UNSC), the African Union (AU) and the European Union (EU).

The letter said that urgent action is needed to halt the deepening humanitarian crisis in the North African country, which erupted after the army ouster of Morsi in 2013 led by former military chief and current President Abdel Fattah el-Sisi.

Since that incident in July 2013, the Egyptian administration has engaged in the “willful killing of thousands of peaceful demonstrators, widespread torture, overt repression of journalists, the unlawful detention of thousands, the imposition of mass death sentences of political prisoners and the execution of detainees following grossly unfair trials,” the letter added.

It also called on the UNSC to “utilize Article 34 of the United Nations Charter to investigate the situation in Egypt to determine the extent to which the current crisis will act as a threat to regional stability for action to be taken under Article 39."

The letter further urged the AU to determine the extent to which the ongoing crisis in Egypt amounts to "grave circumstances" for the 54-nation bloc to intervene.

It also asked the EU to hold a meeting over the death sentences handed down to Morsi and other Brotherhood members.

"Egypt is rapidly descending towards a humanitarian crisis and the security situation presents a grave threat to regional stability. The increased use of violence and repression is causing a schism between the state and its citizens,” said Tayab Ali, the head of the legal team.

Human rights groups say the Egyptian army’s heavy-handed crackdown on Morsi's supporters has led to the deaths of over 1,400 people and the arrest of some 22,000 others, including some 200 people who have been sentenced to death in mass trials.